Process for the manufacture of polycarbonate-oligomers

Abstract: Polycarbonate oligomers having hydroxy end groups are produced by a melt reaction with bisphenol-A and a basic catalyst. The oligomers may then be reacted with chloro end-group siloxanes in the presence of a solvent and an acid acceptor to yield polycarbonate-polysiloxane block co-polymers. The melt reaction occurs at elevated temperature without the direct use of phosgene gas.

Description: The present invention relates to a method for making silicone-polycarbonate block co-polymers. In particular, the invention relates to a method whereby polycarbonate oligomers having terminal hydroxy groups are produced by a melt reaction of polycarbonate resin with a dihydric phenol in the presence of a catalyst and in the absence of an organic solvent. The oligomers are thereafter combined with polyorganosiloxanes having terminal chloro-organo siloxy groups to produce the block co-polymers. The method employed is effective to produce the block co-polymers without directly using phosgene gas in the final synthesis. A siloxane polycarbonate resin can be made in a two-step process involving first reacting chloro end group siloxane oligomers with an excess of bisphenol-A (BPA), then reacting the resulting phenolic hydroxy end group siloxane with additional BPA and phosgene in a conventional interfacial phosgenation reaction to yield the desired block co-polymer. One such useful polycarbonate-polydimethylsiloxane block co-polymer contains 43 weight percent siloxane units with an average block length of about 10. The material has utility as an impact modifier in blends with polycarbonate resin and as a film used as an interlayer in multilayer laminates of polycarbonate resin sheets and acrylic resin sheets. Typically, these laminates consist of two or more layers of polycarbonate sheet, optionally with an internal layer of acrylic sheet, with the resin interlayers serving as an adhesive and as a spacer to separate the sheets. .In a particular process set forth in Vaughn, U.S. Patent No. 3,189,662, assigned to the Assignee herein and incorporated herein by reference, silicone-polycarbonate block co-polymers are made by phosgenating a mixture of dihydric phenol terminated polydiorganosiloxane and dihydric phenol in the presence of an organic solvent and an acid acceptor. Although the method results in the production of silicone-polycarbonate block copolymers useful in a variety of applications, such as injection moldable thermoplastics and elastomers having improved tensile properties, the method requires the direct use of phosgene gas in the final synthesis. Silicone-poly(arylcarbonate) block co-polymers can be made without directly using phosgene gas in the final synthesis of the block co-polymer as set forth in Evans, U.S. Patent No. 4,920,183, assigned to the Assignee herein. A hydroxyaryl terminated poly(arylcarbonate) oligomer having an average of about 2 to about 1,000 chemically combined arylcarbonate units is interconnected with a chlorine terminated polydiorganosiloxane having an average of about 2 to about 1,000 chemically combined diorganosiloxy units, in the presence of an organic solvent and an acid acceptor. The silicone-poly(arylcarbonate) block co-polymer is recovered from the mixture for example by addition of the reaction mixture to a precipitating solvent such as methanol. Evans et al. '183, also discusses the manufacture of hydroxyaryl oligomers. According to Evans et al., these oligomers can be made by effecting the polymerization of cyclic arylcarbonates in the presence of phenol or bisphenol-A (BPA) as shown in U.S. Patent No. 4,849,502, assigned to the Assignee herein and incorporated by reference. Evans et al. discusses another procedure which can be used to make hydroxyaryl oligomers by the controlled reaction in a suitable solvent of high molecular weight polycarbonate resin with a phenol or polyhydric phenol and a polymerization initiator, such as alkaline metal phenoxide or polycarbonate formation catalysts as set forth in Brunelle et al., U.S. Patent No. 4,644,053, assigned to the Assignee herein and incorporated by reference. Chlorine terminated polydiorganosiloxane can be made by known procedures such as by the controlled hydrolysis of diorganodihalosilane, for example, dimethyldichlorosilane set forth in U.S. Patents Nos. 2,381,366 and 2,629,726. Another procedure which can be employed to make chlorine terminated polydiorganosiloxane is the equilibration of a mixture of diorganochlorosilane and a cyclic polydiorganosiloxane, for example, octamethylcyclotetrasiloxane, in the presence of a metal catalyst such as ferric chloride as set forth in U.S. Patent No. 2,421,653. Japanese patent application no. 60-114576 discloses a process to produce low molecular weight polycarbonates having terminal hydroxy groups produced by the reaction of high molecular weight polycarbonates with hydroxy compounds, e.g. 1,6-hexane diol and diethylene glycol. Although 2,2-bis(4-hydroxyphenyl)propane is disclosed within a long list of possibly useful candidate hydroxy compounds, it is not mentioned as a preferred compound. No disclosure is made in the reference as to the ratio of bisphenol-A to polycarbonate. The reference also fails to disclose reacting a hydroxyaryl terminated polycarbonate oligomer with a polydiorganosiloxane to form a polycarbonate-polysiloxane block co-polymers. Industry is currently seeking simplified processes for producing silicone-polyarylcarbonate block co-polymers with reduced solvents and without the direct use of phosgene gas. The present invention is based upon the discovery that a hydroxy terminated polycarbonate oligomer can be produced by a melt reaction of a polycarbonate resin with a bisphenol-A in the presence of a basic catalyst and in the absence of a solvent wherein the mole ratio of BPA to polycarbonate is in the range of 1:50 to 5:10 and preferably 2:10 to 4:10 and the polycarbonate resin has an intrinsic viscosity of from 0.4 to 1.6 dl/g in methylene chloride at 25°C and a molecular weight of from 20,000 to 100,000, and the basic catalyst comprises at least one member selected from the group consisting of tetrabutylammonium tetraphenylborate, tetraethylammonium hydroxide and tetramethylammonium hydroxide. The hydroxy terminated polycarbonate oligomer may thereafter be reacted with a chlorine terminated polyorganosiloxane in the presence of an organic solvent and an acid acceptor to yield a silicone polycarbonate copolymer without the direct use of phosgene. In a particular embodiment, the poly-carbonate oligomers are combined with silicone compositions to produce silicone-polycarbonate block co-polymers. The invention relates to the solventless manufacture of useful polycarbonate oligomers without directly using phosgene. The oligomers may be relatively short hydroxyaryl terminated polycarbonate oligomers having an average of 2 to 50, preferably 2 to 15, more preferably 3 to 6, chemically combined carbonate units. The polycarbonate oligomers are produced by a melt reaction of a polycarbonate resin with bisphenol-A (BPA), ie 2,2-bis(4-hydroxy-phenyl propane) in the absence of a solvent and without directly using phosgene gas. The mole ratio of BPA to polycarbonate is in the range of 1:50 to 5:10 and more preferably 2:10 to 4:10. As used herein throughout the term polycarbonate, in the expression mole ratio of BPA to polycarbonate, should be understood to mean polycarbonate repeat units in the polymer chain. The polycarbonate oligomers may be reacted with a chlorine terminated polyorganosiloxane having an average of 2 to 100, preferably 5 to 60 and more preferably 7 to 12, chemically combined organosiloxy units in an organic solvent to form the silicone polycarbonate block co-polymer. In the invention, a high molecular weight polycarbonate resin is used as a starting material and is melt reacted with BPA to produce polycarbonate oligomers with hydroxy end groups. The polycarbonate oligomers thus produced may be used without directly using phosgene gas in the final synthesis of the block co-polymers. The terms "polycarbonate resins" and "dihydric phenol" are well known and have been defined in detail in U.S. Patent Nos. 4,960,863; 4,973,665 and 4,999,408, all of which are incorporated herein by reference. The polycarbonate (PC) resin may be one of many available materials having an intrinsic viscosity ranging from 0.4 to 1.6 dl/g in methylene chloride at 25°C and a molecular weight ranging from 20,000 to 100,000. In the examples below, a blend of PC resins having intrinsic viscosities of 0.6 and 1.5 dl/g are used, and the PC oligomers have an average chain length of about 4 carbonate units. The formation of silicone-polycarbonate co-polymers occurs by reaction of the hydroxyaryl oligomers and the chlorine terminated polydiorganosiloxanes at elevated temperatures in the presence of an organic solvent (e.g., methylene chloride) and an acid acceptor (e.g., triethylamine). The order of addition of the reaction is not critical. Reaction temperatures which can be used range from 15°C to 40°C. Recovery of the silicone polycarbonate block co-polymer can be affected by the addition of the reaction mixture to a precipitating solvent such as methanol, or by steam precipitation. The silicone polycarbonate block co-polymer made by the method of the invention can be used as a laminating agent for polycarbonates, and as an impact modifier in blends with polycarbonate and other resins. The polyorganosiloxane material may have a chain length ranging from 2 to 100, preferably 5 to 60 and more preferably 7 to 12. In the examples below, the polyorganosiloxane is a polydimethylsiloxane (PDMS) having an average chain length of 8 to 10 dimethylsiloxane units, also known as D units. In order that those skilled in the art would be better able to practice the invention, the following examples are given by way of illustration and not by way of limitation. Method 1 PC oligomer preparation (small scale) A blend of 300 g of polycarbonate resin (intrinsic viscosity of 0.57 dl/g at 25°C in methylene chloride) and 0.7 g (0.00125 mole) of tetrabutylammonium tetraphenylborate was intensively mixed for 30 seconds in a type FM 10L mixer manufactured by Rheinstahl Henschel AG. To that blend was then added 970 g additional polycarbonate resin of the same grade (total of 1270 g, 5 moles) and 342 g (1.5 moles) bisphenol-A. After thorough blending, that mixture was introduced into a model Z SK-30 twin screw extruder manufactured by Werner Pfleiderer Co. operated at 260°C. The oligomer product exited the extruder as a liquid stream and was collected by quenching in water. The oligomers were characterized by gel permeation chromatography (GPC) (see table). Method 2 PC oligomer preparation (large scale) A blend of 1.36 kg of polycarbonate resin (intrinsic viscosity of 0.57 dl/g) and 6.45 g of tetramethylammonium hydroxide pentahydrate was intensively mixed for 30 seconds as in Method 1. This was repeated, and the 2.73 kg of catalyst-containing blend was then mixed in a ribbon blender with 8 kg of the same grade of polycarbonate resin, 60.9 kg of high molecular weight polycarbonate resin (intrinsic viscosity of 1.5 dl/g) and 19.2 kg of bisphenol-A. The mixture was then melt processed in an extruder as described in Method 1 at a temperature of 277°C. The oligomer product exited the extruder as a liquid stream which was collected by contacting with the chilled stainless steel rolls (two 6 inch diameter counterrotating rolls) of a standard dual roll flaker device. The oligomers were characterized by GPC. Ex. BPA/PC Unit Mole Ratio Resin Grade End Capping (Mole %) Catalyst (Mole %) GPC MW MN Corrected MN 1 1/10 100%PC1 2.3% 0.025% 6300 1400 1620 2 2/10 100%PC1 2.3% 0.025% 3800 700 870 3 3/10 100%PC1 2.3% 0.025% 2400 500 660 4 3/10 25%PC1 0.7% 0.025% 28400 4500 4960 75%PC2 5 3/10 25%PC1 0.7% 0.025% 2500 500 660 75%PC2 6 3/10 25% PC1 0.7% 0.1 1500 500 660 75% PC2 7 3/10 25%PC1 0.7% 0.005% 7700 640 810 75% PC2 8 3/10 25%PC1 0.7% 0.01% 6700 900 1090 75%PC2 9 3/10 25%PC1 0.7% 0.025% 1800 500 660 75%PC2 10 3/10 25%PC1 0.7% 0.025% 2600 550 710 75%PC2 11 3/10 25%PC1 0.7% 0.025% 2600 550 710 75% PC2 12 4.8/10 25%PC1 0.7% 0.025% 2300 500 740 75%PC2 13 3/10 25%PC1 0.7% 0.025% 2700 500 770 75%PC2 14 1.3/10 25%PC1 0.7% 0.025% 8000 700 1340 75%PC2 Examples 1-3 vary the mole ratio of BPA/PC between 1:10 and 3:10. Examples 12-14 show a wider range of BPA/PC mole ratios between 1:10 and 4.8:10, with the amount of catalyst and resin being held constant. Added BPA lowers the molecular weight of the oligomers. Examples 4-6 show that different catalysts cause different results generally. The borate catalyst performed well with the low molecular weight, low viscosity (high end capping) PC1 resin of Examples 1-3, but was not as effective with the high molecular weight, high viscosity (low endcapping) PC2 resin of Example 4. The tetramethylammonium hydroxide (ammonium based catalyst) does not exhibit the same variation in results as the borate catalyst. Examples 5-9 show an effective range of ammonium based catalyst, with Example 9 being about optimal for the conditions shown. Molecular weight goes to a minimum at about 0.025 mole percent catalyst. Additional catalyst causes yellowing. Basic catalysts of various well known kinds may be used in effective amounts, for example, about 0.005 to about 0.1 mole percent to achieve the desired results. The present invention employs polycarbonate as a raw material to produce polycarbonate oligomers in an extrusion reaction without solvent or phosgene. The oligomers are combined with siloxanes to produce desired polycarbonate-siloxane co-polymers. While there has been described what at present are considered to be the preferred embodiments of the present invention, it will be readily apparent to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is intended in the appended claims to cover such changes and modifications as fall within the true spirit and scope of the invention.

Claims: A method for making polycarbonate-oligomers comprising: melt reacting a polycarbonate resin and bisphenol-A (BPA) in the presence of a basic catalyst and in the absence of both a solvent and phosgene to produce a hydroxyaryl terminated polycarbonate oligomer having an average of 2 to 50 chemically combined carbonate units, wherein the mole ratio of BPA to polycarbonate is in the range of 1:50 to 5:10, the polycarbonate resin has an intrinsic viscosity of from 0.4 to 1.6 dl/g in methylene chloride at 25°C and a molecular weight of from 20,000 to 100,000, and the basic catalyst comprises at least one member selected from the group consisting of tetrabutylammonium tetraphenylborate, tetraethylammonium hydroxide and tetramethylammonium hydroxide. The method according to claim 1, wherein the polycarbonate oligomers have from 2 to 15 carbonate units. The method according to claim 1, wherein the polycarbonate oligomers have from 3 to 6 carbonate units. The method according to claim 1, wherein the mole ratio of BPA to polycarbonate is 2:10 to 4:10. The method according to claim 1, wherein the catalyst is present in a range of from 0.005 to 0.1 mole percent.

Inventors: ROSENQUIST NILES RICHARD, ROSENQUIST, NILES RICHARD
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1994
Main classification: C08G64
IPC codes: C08G64, C08G77, C08G81